ENVIRONMENTAL SCIENCE AND ENGINEERING (BCE101)
Requirment of Human Being :‐ ‐ Energy ‐ Water ‐ Food
Quantitative & Qualitative
Environment Engineer’s Work – → To provide good quality of water (Water treatment plant) → Waste water treatment → Control on Air Pollution to Maintain the Air Quality (Temperature, Pressure, Wind, Moisture) → Control on Water Pollution → Solid Waste Management (Storage, Separation & Transportation)
1‐Book Environment Engineering By Gerard Kiely 2‐H.S. Peavy D.R. Rowe G. Technobanog Lous 3‐ Water Supply Engineering by S.K. Garg
1.1
Ecological Perspective:‐
→ The environmental engineer is interested to use the varies physical resources such as natural energy (waves, wind, minerals, hydroelectric) and water for domestic & living purpose. → Therefore, It has to understand the functioning with the living system and its interaction with the environment. → Environment – (or Ecosystem) It consists of four major element such as (i) Land (ii) Water (iii) Air and (iv) Living Organism (Plant & Animals) Environment (Ecosystem)
Physical Environment (Abiotic)
Biological Environment (Biotic)
Living Organisms (Planteanimals, Viruses, Bacteria, Fungi) Hydrosphere Lithosphere Atmosphere (Water over the earth (Solid earth & soils) (air upto a distance & inside the earth) of 700 km.) → Living organisms are dependent on each other & depends on the physical environment. Ex.
Plans grow on land & in water. Herbivorous animals use the plant as food. Carnivorous animals eat herbivorous animals.
1.2
Value of Environment :‐ or Resources Natural Resources
Renewable (Energy from sun, water and Biological cycles) It is recycled & reused.
Non‐renewable (Fossil, Fuel, Minerals etc)
Forest Plantation
They are not Replaced. Amount are finite.
Abstract (Animal, plant and natural sight used for tourism) 1.3 Environment Auditing:‐ Listing of all the resources of an area Different types of developmental work go ahead in an area depends on the economical consideration. It has to restrict the economy (money) cased. Therefore, We have to audit or make a list of all the resources of the area. (Environmental auditing) Auditing No’s of species (Living organisms) exist Uses of the living environment.
Direct uses
Indirect uses
Food, Industrial & Commercial products, tourism, medicines etc. 1.3.1 Direct use Food – Plants or domesticated animal products Industrial & commercial products: ‐ Mineral, fossil, fuel, wools, cotton, jute, rubber etc. Medicines‐ 1.3.2 Indirect Uses 9 Biodiversity is the biological processes themselves that provide the value. It is regarding about indirect uses of environments. 9 Environment consists of populations of species‐with air, water, land.
Population of one species (Environment) Biological
mixed together with other
Process helps
species
The entire system.
Communities Many communities are Combined Landscape
9 Therefore, biodiversity is a basic resource which acts as a human – life support system. 9 Biodiversity Sail formation, waste degradation, air & water purification, solar energy absorption, and maintenance of hydrological cycles etc.
Loss of Biological resources Reduction of one common species. 1‐ Depletion of a once – common species 2‐Local or global species extinction 3‐ Ecosystem disruption Environment may be changed due to habitat destruction extinction means the potential of the particular species to be appeared in future.
1.4.0 →
Cost‐Benefit Analysis:‐ After environmental auditing, we have to calculate the cost for the developmental work.
→
Some of the environmental process or services are excluded from the calculation such as: 9 Pollution absorption by biotic system 9 Ecosystem stability 9 Recreational value
9 Historic importance.
→
Environmental parameters to be incorporated is based on World Conservation Strategy (IUCN, 1980).
1.5 Biotic Component:‐ → Everything in the global environment is in one component can affect many others over space & time. → Six major levels of ecological organization are recognized 9 Individual (Physiological functions) Single species 9 Population (Birth, death, population growth rate) 9 Community (Interaction between different species) Both plants & animals 9 Ecosystem (Interaction between living & (biotic) Non‐living component.) A biotic Biotic Community of Living
Hydrosphere (Water)
Lithosphere
Atmosphere
(earth, soil)
(Air)
A Biotic Fig‐1 Interactions between various component → Energy flow occurs at the level of Ecosystem
9 Biomes:‐ Environmental conditions are similar in different parts of country. Ex climate. Vegetation type. 9 Biosphere:‐ Part of earth & atmosphere in which life exists. (Lithosphere, Atmosphere & Hydrosphere comes into contact in Biosphere)
1.6 Ecosystem Process:‐ → Ecosystem is the interaction between biotic & a biotic components (Fig‐1). → Process occurred at ecological level are 9 Energy flow 9 Nutrient cycling
1.6.1 Energy Flow → Interactions between living organism & environment is because of requirement of food which supply energy to survive
→ It also helps to construct body tissues & games for reproduction of species. (child/next generation) Energy sources – converted →1‐ Light energy chemical energy (stored in living organism)
Solar energy Sun (ultimate sources of energy) →2‐ Energy in Environment Autotrophic Heterotrophic
(Energy originated From primary production in other ecosystem.) two – ways 1‐ Production of energy by green plants in presence of light through the process of photosynthesis. 2‐ By sulphur – oxidizing bacteria in deep sea ecosystems.
Photosynthesis → Gran plants create their own food through a series of chemical reactions. 12H2O+6CO2+Light ChlorophyII+enzymes Water 709 kcal C6H12O6 + 6O2 + 6H2O Carbohydrate (to air) (Glucose) + Sugar molecules.
→ Photosynthesis is carried out in day light in leaves & in stems of some green plants.
→ Plant require inorganic substance like 9 9 9 9
Nitrogen Phosphorus obtained from soils. Magnesium Iron
→ Glucose + chemical reaction Fat, Proteins & Nucleic acid (used to form body tissues) Primary production – Production of organic matter by plants. → When any organism requires energy, the reverse reaction to photosynthesis occurs, celled respiration. C6H12O6 + 6O2 metabolic enzymes CO2+H2O+Energy for work
Primary Production →The production of organic matter by plants is called primary production. →The rate of photosynthesis & primary production plays a vital role in the ecosystem. Therefore, It has to consider the amount of primary production in different ecosystem. Net primary production = Gross Primary production – respiration →Gross primary production is the total amount of chemical energy stored by plants per unit area per unit time. →The primary production is affected by the environmental factors, 9 9 9 9
Water Light Soil nutrients Temperature.
Food chain → Autotrophs (plants) can create their own food, but heterotrophs cannot. (animals) →Heterotroph directly or indirectly depends on primary source of food.
Primary production plant (chemical energy)
Photosynthe sis
respiratory
Net production
+ Organic matter (Gross Production) Herbivore to s Carnivores
1.6.2 Decomposition & Nutrient Recycling → Nutrient :‐ amino acids, minerals, sugar, salts & vitamins. → With flow of energy through food chain, nutrients are passed from one – organism to another during feeding.
Autotroph Organic matter Sunlight
Photosynthesis
Respiratory
Sun’s energy R Primary producer R Decomposer Primary consumer Secondary consumer R
R Fig‐4 Energy flow
Soil
Rain
Plant
Primary product
Primary consumer
Decomposer
Herbivores
Secondary consumer
Carnivores
Fig 5 Nutrient cycle
1.7 Environmental Gradients & Tolerance :‐ → Each species is not found in every type of habitat (area) → Uneven distribution of organism → This is because of several factors 9 9 9 9 9 9 9
Light Temperature PH Food Water Shelter Predictor & competitor’s interaction.
→The above environmental factors varies from the equator towards north or south; is called environmental gradient. →The plot between environmental & population size is called tolerance carve. ++++++++++++ A = Species absent B = Low population
Range of optimum:‐ Area of greatest numbers.
Concept of Hydrology 2.1 Hydrological cycle:‐ Water evaporates from oceans & other water bodies, and from land surfaces. The evaporated water rises into the atmosphere until the water vapour condness. Then the condensed water vapour condenses. Then the condensed water vapour in the form of rain & sometimes as snow. ++++++++++++++++
Fig – 2.1 Hydrological cycle. 2.2 Water balance:‐ →The accounting of water for a particular catchment, region or earth is called water balance. →Therefore, water balance is the account of hydrological cycle. Moreover, the input to the hydrological cycle is due to precipitation. →the equa for water balance is
P = R + E S G
P = Precipitation, mm/day R = Stream runoff E = Evaporation S = Change in soil moisture status G = Change in ground water status 2.3 Energy budget/balance:‐
The source of energy is solar radiation. Earth surface absorbs solar radiation. The energy absorbed by earth surface is reflected back to the atmosphere & some enters into the earth. Furthermore, the earth also re‐radiates some solar‐energy. →The energy balance is the accounting of distribution of the solar radiation through atmosphere and onto the earth’s surface of land and ocean. Moreover, It accounts for the outgoing terrestrial radiation from the earth’s surface. →It includes evaporation flux, sensible heat flux & net radiant emission by surface. →Our interest is find the net‐incoming radiation at the earth’s surface. Quantity of radiant energy remaining at the earth’s surface. Rn = LE + H + G + PS + M Where Rn = Specific flux of net incoming radiation, W/m2 L = Latent heat of vaporization (Doesn’t increase the temperature) E = specific flux energy of sensible heat into the atmosphere (watt/m2) G = Specific flux of heat into or out of the soil PS = Photosynthetic energy fixed by plants M = Energy for respiration & heat storage in a crop canopy. → Neglecting PS & M, we have Rn = LE + H + G 2.4 Precipitation:‐
→ Preciption is in the form of rain, hail or snow. We are interested to determine the amount, rate & duration of precipitation. → The magnitude of rainfall is determined by three ways such as:
9 Precipitation gauges 9 Rader Instruments 9 Satellite remote sensing
→ Precipitation can be calculated from different method analysis results i.e. 9 Area precipitation 9 Dept – area – duration analysis 9 Precipitation – duration – frequency analysis. 9 Intensity – duration – frequency analysis. 9 Extreme values of precipitation. Area precipitation → P1 = .dx
Mean area Total accumulation Precipitation of precipitation at all point ‘x1’ in the catchment → Time averaged main area precipitation M P2 =
I = 1A A Total precipitation at ‘x’ & time ‘ti’. Where A = Catchment area T = Total storm period. Depth – area – duration analysis. → Generally, as the area of a catchment increases, the depth of precipitation decreases. Therefore, an area reduction factor (ARF) Is used for precipitation in this analysis. Precipitation frequency → Rainfall record over a period of time with a specific magnitude. (No. of times) +++++++++++++++++
Fig 2.3 Depth – area – duration curve Intensity – duration – frequency analysis (IDF) → From IDF curves, as rainfall intensity increases, its duration decreases i.e. I Runoff (Q) = CIA Catchment area (km2) Locality constants. 2.5 Infiltration:‐ →It is the movement of water from soil surface into the soil. About 76% of precipitation infiltrate into the soil.
1‐ The properties of soil which responsible for infiltration are
9 Bulk density 9 Particle density 9 Porosity 9 Volumetric water content 9 Degree of Saturation. Bulk density of a soil is: ( b)
∫b = ( ) Md = Dry mass of a soil volume Vt = total volume (Undried condn)
Particle density (∫m) = Vd = dry volume Typical value for most sails is 2.65 kg/m Porosity (Ø) = = 1 ‐
Va = volume of air Va = volume of water Vs= volume of solids
Volumetric Water content (θ) = =
Degree of saturation (S) is the proportion of water containing pores. of the measure of wetness. S = = → Soil horizons and Hydraulic conductivity Hydraulic conductivity is the rate of movement of water into the soil. Dead leaves →vegetation (Grass, tree) Soil
Unsaturated zone A ‐ Horizon Sub‐soil
B ‐ Horizon Saturated soil C – Horizon Bed Rock 3‐Soil – moisture content or soil – water content →Each soil has a maximum moisture magnitude/capacity, when it is saturated. +++++++++++++++ Aeration zone: ‐ is the upper zone where the pores are occupied by air. Capacity zone: ‐ is the zone through which water will rise through the soil pores by capillary action. Ground water zone :‐ exists below the water table.
2.6 Evaporation & Evapotranspiration:‐
→Evaporation is the process by which water is returned to the atmosphere, from liquid & soild into the vapour state. →Evaporation into the atmosphere occurs through the transpiration of leaf parts of plants. The process is termed as evapotranspiration. →30% of rainfall flows in the form of runoff. Therefore, on the ocean surface of earth there is more evaporation than precipitation. →The type of evaporation/evaporatranspiration are: 9 Evaporation from lake surface (Eo) 9 Actual evapotranspiation, (ET) 9 Potential evapotranspiration (PE) Evaporation from lake or open water body surface. It includes the evaporation & transpiration from a land surface, & vegetated. It will vary depending on the present soil – moisture status. →Potential evapotranspioration is determined for catchment research projects, when radiation & heat balance are considered. →Factors causing evaporation from any surface are: 1‐ Latent heat of vapourization & (2) wind 2.7 Ground water:‐ →Ground water is defined as the water below the water table.
The level of soil below which the pore space is 100% occupied by water. 2.7.1 Aquifers Water table +++++++++++++++ →An aquifier is a water – bearing rock formation that contains sufficient amounts of water to be exploited & brought to the surface by wells. →Aquifers are two types in nature: 9 Contined 9 Uncontined →Upper aquifer is unconfined & it has a natural water‐table‐line. Free to move up & down →The impermeable strata between unconfined aquifer & confined aquifer is called aquaclude. →When wells are drilled into confined aquifer water will rise & attain its own ‘water table line’. 2.8 Ground water chemistry:‐ (quality/properties)
→The quality of ground water depends on the subsoil & rocks that it passes through. Ex:‐ hardness, iron, manganese
1‐ Hardness When Ground water pass through the limestone, it dissolves/mixed with calcium & magnesium compounds; which cause hardness. (200 to 400 mg/litr) 2‐ Iron & Manganese →Excess amount of irons don’t cause health problem (Taste problems) →It will give a metabolic taste to water. →Manganese cause a black discoloration of water. →Iron & manganese are good indicator of water pollution. 3‐ Hydrogen sulphide (gas) →H2S is present in water from rocks like limestones or shales. →It create the same problem as in the case of Iron. 4‐ Sulphate (800 mg/lit) 5‐ Sodium Chloride (Nacl)
→This problem occurs in areas where rocks are highly permeable. 2.9 Ground water contamination:‐ internet Make impure which will become harmful →The indicators of the source of contamination are E.coli, nitrate, ammonia, potassium, chloride, iron, manganese etc. 1‐ Bacteria & Viruses. → E. coli is the parameter which indicates the presence of bacteria & viruses. →Presence of bacteria in ground water causes typhoid fever, diarrhea, gastrointestinal infection etc. →E coli Bacteria – From septic tank effluent, landfill sites & birds etc. 2‐ Nitrate →Nitrate rich water cause mathaemoglobinaemia (blue baby syndrome) to young children. 3‐ Ammonia →It has a low mobility in soil & sub soil. 4‐ Potassium (K) →It is immobile in soil.
5‐ Chloride (Cl)
6‐ Iron & Manganese 2.10 Ground water pollution control/prevention:‐ Water Quality Requirement :‐ 3.1 In – Stream Standards:‐ → Water quality requirements & water quality standard. → Many factors affect stream‐ Quality ex:‐Waste water discharge & human activities 3.2 Portable – water standard:‐ +++++++++++++ 3.3 Waste‐water effluent standards:‐ Decomposition: ‐ The process of decay caused by bacteria & fungi ‐:Water Quality in Rivers :‐ 4.1 Organic content parameter DO & BOD in streams →DO – Dissolved oxygen. →Water bodies support a variety of fish and animals. They require oxygen & a stream/river must have a minimum dissolved oxygen about 2mg/litr.
→ When an organic waste is discharged to a stream, the organic content undergoes biochemical reaction. This reaction a consumes oxygen from water bodies. Organic content + O2 micro‐organism New+Co2+H2O+stable products Biomass → The amount of dissolved oxygen used up from water sample by micro‐ organism for the bio‐chemical reaction is termed as BOD. → The relation between DO & BOD is developed by Stricter & Phelps model. Follow = K1 Lt – K2 DO other book =
K1 L0 e‐K1t – K2 DO
Lo = Oxygen demand at t= to Lt = C BOD (mg/Litr) = Carbonaceous bio‐chemical oxygen demand amount of oxygen Remaining at time ‘t’ Constants K1 – dexygenation rate (1/day) K2 – reaction rate (day‐1) (Lo‐Lt) – Oxygen consumed.
The dissolved oxygen (Do) decreases in a river/stream by degradation of BOD. The variation of DO in the stream/river w.r.t BOD was derived by Streeter & helps model. Seeded water – Deoxygenation – Chemical Oxygen Demand (COD) :‐ A quick chemical test to measure the oxygen equivalent of the organic matter content of waste water that is susceptible to oxidation by a strong chemical. (organic & inorganic) (both) Or COD is a measure of the total organic carbon with the exception of certain aromatic such as benzene which are not completely oxidized in the reaction. Organic materials such as cellulose, phenols etc. resist biodegration along with pesticides & these materials are oxidized in the COD test. * The organic content of a waste water stream is determined by following tests.
BOD5 :‐ conc. Of ‘Do’ at day ‘5’ – COD TOC:‐ Total organic carbon, at day – ‘O’ at day – ‘5’ BOD5 = P(DOi – Dos)
Dilation factor. 4.2 Transformation process in water bodies:‐ The constituents in water – bodies are DO, BOD, temperature, salinity, nitrogen (as organic, ammonia & nitrate etc), phosphurs etc, (considering water quality). → The transformation process in water bodies are: 1‐ Influent ‘clean’ flows 2‐ Influent ‘waste’ flows 3‐ Biological oxidation of carbonaceous & nitrogenous organic matter. 4‐ Reparation of surface layer 5‐ Reduction of BOD (sedimentation) 6‐ Photosynthesis 7‐ Respiration 8‐ Oxygen diffusion 9‐ COD (Chemical oxygen demand) 4.3 Transport process in waterbodies:‐ → Transport processes are 1‐ Advection (heat, humidity & solidity in ocean) 2‐Difusion :‐ the process by which models See S.K. Garg intermingle as a result of their & other Book ex‐ two gases‐mix K.E. of random motion. For destination
with costively of the process 3‐Buoyancy :‐ is an upward for exerted by fluid that opposes the weigh of immersed object. 4.4 Stricter – Phelps Oxygen Sag Model :‐ → The rate of decomposition of organic matter is proportional to the amount of organic matter available ; i.e.
= ‐ K ‐ 1 ‐ 1 1 Lt ‐ Lt = BOD remaining at time ‘t’, K1 = deoxygeneation rate coefficient per day Integrate equation 1‐ between (Lo) to (Lt) Lt = Loe‐k1t We have ‐‐‐‐‐‐‐‐‐‐‐ 2
Where Lo = Ultimate BOD = (BOD at tint – “O”) = initial BOD → ‘BOD’ consumed at time ‘t’. (BOD)t = Lo‐Lt = Lo – Lo e‐K1t = Lo (1‐e‐K1t) Solve Ex – 7.1
7.3 → When biodegradable waste was discharged to a stream/river, It consumed oxygen. The deticieny of dissolves oxygen is maintained through reaertion from atmosphere. Hence, eqa 1‐ can be written as = K1 Lt – K2(DO) = K1 Loe‐k1t – K2(DO) ‐‐‐‐‐‐‐‐‐‐‐ 3 Where DO = DO deficit (oxygen deficit). = maintain DO – actual DO Lt – Oxygen remaining at time ‘t’ K1 – deoxygenation rate per day K2 = reparation rate per day → Integrating eq, we have DO(t) = (e‐k1t‐e‐k2t) + DO e‐k2t ‐‐‐‐‐‐‐‐‐‐ 4 Where Lo= Oxygen demand at t = to Doo = dissolved oxygen deficit at t = to Dissolved oxygen saturation deficit at any time‘t’.
→ Equ 4 is the streeter – Phelps oxygen sag formula. → Solve ex 7.5 Initial DO ……… DOc DO sag curve Deficit min Reaertim DO (mg/lit) deoxygenation time Fig Dissolved oxygen sag curve Doc → Minimum or maximum dissolved oxygen deficit → differentiate equ 4 w.r.t to ‘t’ & set it equal to zero. We have ‐ tc = . Ln 1‐ time of occurrence of minimum DO or maximum dissolved oxygen deficit DOc = DO(t) ‐ DOo Dissolved oxygen saturation deficit at time. Chemical Pretreatment: ‐ to remove undesirable properties of water (excess colour of algae) Photosynthetic alghe. (doubt) Unit (NTU:‐ Nephelonetric turbidity unit) Prechorinctin for (Low turbidity water)
Activaled carbon (Turbidity: Should be 0.3 melm/min) → Water is recycled through the plant. → Filtration operated on hydraulic principle. Vf = Vt x f4.5 Porosity Terminal velocity to wash medium from bed 5.2.4 Disinfection – → It refers to operations used to kill pathogenic microorganisms. → Sterilization is the process for the complete destruction of all living matter. → Disinfection doesn’t indicate to sterilization process.
→ 90% of bacteria & viruses are removed by coagulation & filtration process. → The rate of destruction of micro organism is alchemical reaction (chick’s law) = ‐kNt solun ⇒ Nt = No e‐kt Nt = No of organisms at time ‘t’ No = K = rate constant of the type of disinfectant, micro‐organism → The common used disinfectants are 9 Chlorine dioxide. 9 Chloramines 9 Ozone 9 Ultra‐videt radiaction 9 Chlorination. 1→ Make a short note on the use & effect of different disinfectants. 2→ Draw the layout of the water‐treatment plant.
* Brak‐point Chlorination :‐ Due to the reactivity of chlorine, it reacts with a multitude of inorganic & organic materials present in water. In some cases, it is used as an oxidizing agent first to break down these materials. This type of chlorination is called ‘breakpoint’ chlorination. Due to high dosages of chlorine normally employed, this procedure is no longer performed in Germany, but still widely used in US & other countries.
‐: Waste‐Water Treatment:‐ 6.1 Waste water characteristics:‐ → Waste – waters are either from the sourc of industrial waste‐water or from municipal waste water. → Components of waste water are suspended solids, biodegradable organics, and pathogens. → Suspended solids are organic in nature. Ex Body waste, food waste, paper & biological cells. → Soluble organics in wastewater are of proteins, carbohydrates and lipids. → Water‐borne pathogens may be found in domestic wastewater. 6.2 waste water treatment processes:‐ → Domestic & industrial waste‐water contain mainly organic waste.
→ So, the main treatment processes are used towards organic removal. → Process are: 9 Pretreatment 9 Primary treatment 9 Secondary treatment 9 Advanced treatment 6.3 Pretreatment:‐ → The floating debris destination product of building debris & grit, & oily dictionary scums are removed from waste‐ Vegetation prolent water, in the pretreatment process‐ → Sometimes, the pH of waste‐water is in such a range that water is either too acidic or too alkaline for optimum biological degradation. It need pH correction. The PH correction is achieved by the addition of sulphuric acid (H2SO4) or lime. 6.3.1 Screening → The objective of screening is to remove large floating material & so protect down stream mechanical equipments. 9 Corase screen with opening (remove large material > 6mm) 9 Fine screens with opening (1.6mm to 6mm material) (For activated sludge) 9 Very fine screen opening (0.2 to 1.5mm) 9 Micro screen with opening (0.001 to 0.3mm)
Municipal waste water
screens
Grit facilities
Fat, oil, greases FOG flotation
Balancing pH, Organic, nutrient
Primary treatment
6.3.2 Grit channels – → Grit is inorganic sand or gravel particlesd of size about 1mm. They are washed into sewer collection‐systems from road & pavement. → Grit does’nt exist in industrial process of waste‐water. → Grit can abrade mechanical equipments.
→ Grit collection devices are: 9 Helical flow aerated grit chamber 9 Horizontal flow grit channel. Air enters one side of channel near the bottom & this cause a spiral motion Iar to the main flow direction.
Air supply
Grit Fig Helical flow aerated grit channel → Heavier grit particles settle while the lighter organic matter remain in suspension. → Aerated grit chambers are more efficient than horizontal flow type. → The design of grit channel is based on setting of particle F1 = FD
⇒ (γs – γw) V = CD As fw ⇒ Vs = (Sp‐1)d2 Sp = Specific gravity of participles CD = drag coefficient = V = Kinematic viscosity = Ex 12.4 Design a horizontal flow grit chamber to remove grit of size greater than 0.2 mm if the through flow is 10,000 M3/d. the specific gravity of the particles is 1.9. Solution Setting velocity (Vs) = . (
‐
p
)d2
w
= x (1.9‐1) x (0.2)2 = 19.6 mm/see = 0.02 m/see Assume Depth (D) = 1.5xwidth (w)
C/s area = A = WxD = 1.5w2 A = = = 0.39m2
6.3.3 Flotation :‐ Flotation is used when suspended particles have low setting velocity that they are not settleable in sedimentation tank. → Sedimentation, in water‐treatment chapter, is the gravity unit process of separating solids from liquids. → Flotation is the buoyancy unit process of separating ‘solid’ particles from a liquid phase. → In municipal work, solids are fats, oils & grases (FOG). → The process of separation involves introducing air bubbles at the bottom of a flotation tank.
+++++++++++++++++++++++++++++++++++ Fig: Dissolved Air Flotation → Air bubble attaches with particulate (composed of dist unit particles) dictionary) matter & the combined buoyancy helps the particle to rise to the surface. Then, it is removed by skimming. Dictionary.
9 Gravity flotation 9 Vacuum Make a short note 9 Electro flotation 9 Dissolved air flotation (DAF) 9 Air flotation
6.3.4 Equalization :‐ Uniformity/balancing → Waste‐water treatment plant receives the waste matter (effluent), uniformity/balancing is required for that. → This includes 9 Flow equalization 9 Organic equalization 9 Nutrient balancing 9 PH balancing (PH correction) (6.5 to 8.5) → Flow equalization/balancing operates & balanced 7 days. Overflow Raw Screens structure To primary 2 3A 1 sedimentation Waste water Grit removal
3B
4
Equalization Flow control
6.4 Primary Treatment :‐ → Primary treatment is often called clarification, sedimentation or setting. → The waste water is allowed to settle for a period (about 2hr) in a setting tank and produce clarified liquid effluent in one stream. → Therefore, the objective is to produce a suitable for the secondary biological treatment & achieve a solid separation. → Hence, the primary treatment include 9 Reduction in suspended solids 9 Reduction in BOD 9 Reduction in the amount of waste‐activated‐sludge (WAS) 9 Removal of floating material. 9 Partial equalization of flow rates & organic load. ++++++++++++++++ Fig C/s of a typical circular primary clarification tank. 9 Waste‐water enters through the diffusion‐box. The tank is sized so, that the retention time is about 2hr. in this period, the suspended particles settle down as sludge & lift upwards through a central hopper. 6.4.1 Chemically enhanced primary sedimentation → The addition of coagulant chemicals
(iron, salts, lime, alum) Before sedimentation makes the suspended fine particles into settleable flocs. → This process increases. The efficiency of suspended solid & BOD removal rates.
+++++++++++++++++++++++++++++++++++++++++++++++ Surface overflow rate m3/d/m2) → → As the surface overflow rate increases, the removal efficiency decreases. → The mechanism of chemically enhanced primary sedimentation is to use an aeration tank & add coagulants. 6.4.2 Sludge quantities from primary setting:‐ → The amount of sludge produced during primary setting will depend on the total suspended solids & the efficiency of solid – removal. 6.5 Secondary treatment :‐ → In primary setting process. About 60% of suspended solids & 30% of BOD removed from west‐water. → The purpose of secondary treatment is to reduce the BOD which does not benefit as much as suspended solids from primary setting. → Secondary treatment process produces non‐polluting and products from the
(H2O, CO2, Sludge) Biodegradable organic matter:‐ → The end product shouldn’t provide a food source for aerobic bacteria. (Liquid efficient) → The removal of organic matter includes the processes: 9 Bio‐degradation 9 Air‐stripping :‐removal of covering 9 Adsorption (accumulation of molecules particles to form a thin film on surface of water) 9 Activated sludge system 9 Attached growth system 6.5.1 Activated sludge system → The common activated sludge systems are 9 Complete mix reactors. 9 Plug flow reactors. 9 Oxidation ditch 9 Contact stabilization 9 Sequencing batch reactors Complete Mix Reactors ‐
→ It has uniform characteristics throughout the entire reactor. → Aeration is provided by surface aerators. → Dissolved oxygen (DO) levels are maintained throughout the process (2mg/L). → The returned activated sludge (RAS) from the clarifier is fed directly to the aeration basin bacteria Organic + O2 CO2+NH3+new biomass Olio d Process Plug Flow Reactors ‐ → Plug flow means a ‘plug’ of substrate influent to an aeration basin is moved forward, without too much interaction with plug. This means satisfacting mixing occurs in the lateral direction, but none in longitudinal direction. Influent Effluent Plug → There is a high organic loading at the influent end of the basin. → There is an excess of food substrate at the influent end shortage of food substrate at the downstream end. → Through the aeration basin the food substrate. Decreases while micro‐ organism concentration increases. Oxidation Ditch – +++++++++++++
Fig Layout of an oxidation ditch system. Contact Stabilization – → Aeration is carried out in two phases in two different tanks. → Influent effluent Contact tank
Clarifier
Sludge‐ sludge waste recycle, Aerator tank → In contact tank the suspended organic matter is adsorbed by the microbial mass and the dissolved organic matter is absorbed by the biomass. Sequencing batch reactors‐ → It is a complex mix activated sludge system without a secondary clarifier. → Five different sequences are followed within the single aeration basin. → Aeration & clarification are carried out in one tank.
++++++++++++++++++++ 6.5.2 Attached growth systems (Write a short note) → It allow a microbial layer to grow on the surface of the media (stone, plastic) → It exposed to the atmosphere from where it draws its oxygen. → The microbial layer is sprayed with the waste‐water.
→ In this process, the microbial layer convents the biodegradeable organic waste‐water to biomass & by – products. Microbial :‐ involving/caused by microbas → The microbial layer helps to reduce the BOD of effluents. Percolating Filters – (Tricking Filters) → These are generally cylindrical or rectangular boxes of concrete or steel, containing stone media. → The media is angular rather than rounded (ex limestone is a better choice). → The floor of the tank has an underdrain system for collecting the underdrain system for collecting the treated waste water.
Q.1‐ Operation of tricking filter with diagram. Factors affecting the efficiency of a tricking filter.
Granular media filtration:‐ → The media may natural/synthetic media & filter type is either of pressure or granting. Adsorption :‐ (Activated carbon adsorption) → Organic compound may be removed by PAC or granulated activated urban (GAC). Powered. Chemical treatment :‐ In this process, the PH of effluent rises to 10.8 – 11.5, so that ammonia (waste water) Nitrogen converted to ammonia gas & it released to atmosphere.
++++++++++++++
6.6 Secondary Clarification :‐ → The retention time in secondary clarificator is about 2 hrs same as in primary clarification. But it is provided with a deep setting tank. (about 4.5m) → The aim is that no solids should ‘escape’ in the clarified effluent. → The solids are biological in nature. (Biodegradable organic matter) It may require oxygen demand from water body for the decomposition. → The important parameter for secondary clarification is surface overflow rate (SOR) = → discharge Area of C/S 6.7 Advanced Treatment Process – (Filtration) 9 Granular media filtration :‐ It composed of one type of grains 9 Adsorption (Sand/stone ek) 9 Chemical treatment 9 Air stripping Removal of ammonia; 9 Chlorination when ammonia levels are high in effluent (waste water)
6.8 Wastewater Disinfection – → The objective of disinfection is to eliminate pathogenic organisms. → The disinfection producer for wastewater are ? 9 Chlorine 9 Ozone
9 Chlorine dioxide 9 Ultravidet radiation.
6.9 Layout of wastewater treatment plant – +++++++++++++++++++++ Fig layout of a typical wastewater system including filtration.
‐: Anaerobic digestion :‐ Process of decomposing the organic matter. 7.1 Introduction :‐ → It is used for the treatment of industrial, agricultural & municipal wastewater.
→ Anaerobic digestion is the use of micro‐organisms for the stabilization of organic (in the absence of oxygen) matters to the form of methane and other inorganic products.
Organic matter + H2O microbial CH4 + CO2 + organism
New + NH3+H2S+Heat Biomass → It occurs in the absence of oxygen. → Concentrated waste‐water sledges may react with waste‐water & hena, can produce bad‐products or gases to the environment.
Therefore, It has to make the sludges as inert prior to disposal. The common No reaction with water or other elements. No reaction with water or other elements. Process is biological degradation. This process convert the solids to non‐cellular end
products. (dictionary) Not divided into cells The process is commonly termed as sludge digestion. 2‐ Sludge digestion reduces the volume of thicken sludge as well as makes the remaining solid as inert. Aerobic digestion Anaerobic digestion Aerobes: ‐ Micro‐organisms require oxygen for their survival, are called aerobes. Anaerobes: ‐ Other micro‐organisms can’t survive in the oxygen environment, are known as anaerobes. 3‐ Primary sludge contains large amounts of available organics that would induce a rapid growth of biomass if treated aerobically. (dictionary) total mass of living matter 4‐ Anaerobic decomposition produces less amount of biomass compared to aerobic processes. The aim of anaerobic digestion process is to convert as much as sludge to end products such as liquids & gases; while producing a little residual biomass.
7.2 Microbiology of Anaerobic digestion :‐ → Four different microbiological groups (bacteria) are recognized. 9 Hydrolytic bacteria compound reacts with water & produce other compound.
9 Acidogenic bacteria formation of acid. 9 Aceticlastic Methanogens. 9 Hydrogenophilic Methanogens. Complex waste (sludge)
Protein carbohydrates. Lipids. Hydrolysis Process Hydrologic Bacteria. Aminoacid, sugar
Faltyacid, alcohols.
Acidogenic bacteria Acidogonesis process Intermediate Products.
Acetate H2, CO2
Aceticlastic
Bacteria Hydrogenophilic Methane, Methanogens CO 2
7.3 Methane Proclcetion:‐ → Anaerobic sludge digestion divides into two groups, the acid formers & methane formers. → The influent sludge enters the tank close to the top at the supernatant layer (purified liquid layer) → There is a activity digesting sludge layer below to supertent layer. → Finally the decomposed (digested) sludge stabilized at the bottom of tank.
Gas released. Influent sludge Scam Supernant released. A Activity digesting sludge. Stabilized sludge
Digested sludge Ex C6H12O6 3CO2 + 3CH4
7.4 Application of anaerobic digestion:‐ → Agricultural wastewater treatment Industrial Municipal
‐: Air Pollution :‐ → Man can hardly survive for 5 minutes without air. → However, he can survive 5 days without water & for 5 weeks without food. → When air gets polluted, it causes a number of diseases in human body (animals). → Hence, the polluted air is harmful to all types of life (plant, animals).
8.1 Air pollutants:‐ → The polluted air gets contact with the non‐living materials (metal, wood, stone etc) & corrosive action of polluted air or due to the chemical attack of air pollutants. → Primary pollutants – Sulphur oxides (SO2), carbon monoxide (CO), Nitrogen oxides (NO & NO2), Lead (Pb), hydrocarbons, allergic agents & radioactive substances, H2S, H2F‐, & methyl & ethyl mercaptans. → The primary pollutants react with each other & with water vapour & produces new pollutants, called secondary pollutants. → Secondary pollutants are produced from he chemical reactions due to oxidation caused by energy of sun. → Secondary pollutants are more harmful than the original primary pollutants. The pollutants are: 9 H2SO4 (Sulpharic acid)
9 Ozone (O3) 9 Formaldehydes (H‐CHO) or CH2O 9 Perony‐acyl‐nitrate (PAN) (NOz) 1‐ Sulpher dioxide – (SO2) → It is an irritant gas & when inhaled, it increases the breathing rate & causes oxygen deficit in the body. ex Patients of asthma are affected by this pollutions. → SO2 may oxidize to form SO3, which when inhaled, may dissolve in body fluid to form sulphuric acid (H2SO4). H2SO4 is a very strong corrosive acid. → SO3 causes severe branch spasm. (dictionary):‐ difficulty in exhalation → SO2 originates from refineries & chemical plants, smelting operation & burning of (dictionary):‐ formation metals by heating fulls. Thermal power plant also emits SO2. → The quantity of SO2 in air is 0.03 ppm (Specified Air Standard)* *Contentation of pollutant (Unit of measurement) 9 Generally the concentration of pollutant can be expressed as micrograms per cubis metre (μg/m3) at atmospheric temp & pressure. 9 If the concentration is expressed in cum(m3) per million cum of air, it is called as ppm (parts per million). 9 The relation betwn ppm & μg/m3 is: 1 μg/m3 =
X 103
→ Liter
Mol → molecule ( /mol) → Volume in Liter occupied by one molecule. 2‐ Carbon monoxide. (CO) – → CO has 200 times affinity towards blood hemoglobin (Hb) than oxygen. → When inhaled, CO replaces O2 from haemoglobin & form carboxy‐haemoglobin (COH6). It has no use in respiratory process. Hence, helf of the blood is used → Carbon monoxide is responsible for heart attack. Sources → CO originates from auto mobile exhausts & incomplete combination of organic matter. (dictionary):‐ (Process in which substances reacts with oxygen.) → In cities, the concentration of CO is 54 ppm. → Specified standard (9 ppm). 3‐ Oxides of Nitrogen (NO, NO2)‐ Nitric oxide Nitrogen dioxide. →Eye & Nasal irritations are causes by NO2 (when concentration is 15) → Respiratory discomfort (concentration is 25ppm) → It originates from automobile exhausts:‐ (dictionary) Furnace smokes
→ Specified standard for NO2 is 0.05ppm
4‐ Hydrogen Sulphide (H2S) – → H2S is a foul smelling gas with a odour of rotten egg. (dictionary) – dirty (dictionary):‐Damaged/useless → This gas cause headaches, sleeplessness & pain in eyes. → Higher concentration of H2S may block oxygen transfer & damage to nerve tissues. → H2S is rarely found in atmosphere, therefore, It is not included in the air‐quality‐ standers. (No specified standard‐concentration) → It is produced in industries like oil‐refinibg, rubber, artificial, silk etc. 5‐ Methyl & Ethyle Mecaptans – → Ethyl mercaption :‐ C2H3SH → These compounds are not harmful to us. → They have strong odours. 6‐ Hydrogen Fluoride & Other Fluorides – → All fluoride compounds are extremely irritant gas & corrosive in nature. → Their smaller concentration may produces fluorosis in cattle & plants dictionary – a pathological condition. → It is not harmful to human beings. Sources → They are emitted into atmosphere from aluminum plant, steel plant, phosphate frtiliserplants etc & by burning of coal.
→ Its concentration in city air is very less (around 0.025 ppm). It is not included in air‐ quality‐standard. 7‐ Lead (Pb) – Sources → It is ejected into the atmosphere through exhausted of automobile. (Gas emitted from the automobile engine) → It may cause irritation of mucous‐mucous – membranes of nose, throat & lungs, when (a thin layer inside of nose & mouth & outside of other part of body inhaled air. → It may damage to Liver, kidney & gastrointestinal tracts (systems). (dictionary)‐system. → Specified standard for lead in air‐quality‐standard is 1.5 μg/m3 8‐ Hydrocarbons – (Alkane, Alkene, Alkynes.) → Alkenes are highly reactive in atmosphere through photochemical realn. → It reacts with other pollutant gases & forms new pollutants. Sources → Hydrocarbons released to the tmosphere by automobile exhausts & by smokes of incinerators & from Oil‐refineries. → Hydrocarbons are found to cause body cancers. → Formal‐dehyde cause irritation of eyes, skins & lungs. → Air‐quality‐standard is 160 μg/m3 (0.24 ppm) 9‐ Allergic Agents – → Microscopic substances in air may cause allergic reactions in human bodies, called aero‐allergens. (Physical matter of which thing/person consist)
→ Sneezing, asthma, skin troubles are due to allergic agents. Sources → It Originates from plants & animals. → Finally powered industrial materials may cause allergic reacn with sensitive persons. → Powered like material form seasonal plants. 10‐Radioactive Isotopes – ex Titrium (H‐3) Carbon‐11, 14, 18 → Radioactive emissions leads to anemia, cancers & shortening of life spans & genetic effects. (Its nuclic are unstable & it dispute energy by emitting radiation in the from of ‐,β‐ &γ‐rays) & accidential discharges from atomic & nuclear reactors.
11‐Ozone (O3) – → The presence of ozone gas in air may cause irritation in the respiratory (dictionary) tract. System. → it may be produced by photochemical process
Two pollutants unit together in the presence of sun‐light, producing a third pollutant. → In day time, It is also produced by photochemical realn of hydrocarbons & nitrogen oxide. (in highly motorized areas)vehicle used (dictionary) → The air standard for ozone is 0.12ppm Environment protection agency 8.2 Criteria & Non‐criteria pollutants:‐
→ Criteria pollutants are: 9 9 9 9 9 9
CO NO2 O3 SO2 Lead Particle matter (dia
